Address buffer mode switching for varying request sizes
A plurality of modes is provided for communicating between a host system and a peripheral storage system controller. A first communication mode may be selected from the plurality of communication modes based on a bit length required to communicate a physical address. During runtime, a switch from the first communication mode to a second communication mode may be performed in order to improve the efficiency of processing address requests at the storage system controller.
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This application is related to U.S. Patent Application entitled “Variable Length Command Pull with Contiguous Sequential Layout,” Ser. No. 11/070,131, filed on Mar. 1, 2005, which is incorporated by reference in their entirety.
BACKGROUNDA. Technical Field
The present invention relates to the communication of storage request commands, and more particularly, to providing a plurality of communication modes in which variable request size commands are communicated between a controller and a host system.
B. Background of the Invention
A host processor or device driver communicates with various peripheral devices to control the operation of these devices within the processor's system. One such example is a processor communicating with a memory device, such as a redundant array of independent disks (“RAID”), via a PCI Bus. A controller within the RAID may receive a request, such as a read/write command, from an operating system and perform a corresponding action on one or more drives within the RAID. Typically, this communication between the operating system and memory device occurs in fixed length words that are defined within the system so that both operating system and the controller communicate properly.
One such example is the use of a 32-bit word, sent during a single input/output cycle, in which an address may be provided relating to a particular request. This particular example presents a problem if the system memory size requires a word that is longer than 32-bit in order to communicate a physical address. This problem is currently addressed by effectively patching a longer address within the 32-bit word using standard coding techniques. The encoded address is sent to the controller, which must extract the address using decoding techniques.
This method of communicating coded addresses within a 32-bit word still limits the maximum addressable memory due to the limited amount of information that can be stored in 32-bits. Another common solution is to simply increase the size of the passed address to 64-bits. This option allows addressability of the full address space of today's computer systems, but has the disadvantage or requiring two 32-bit 10 cycles in order to communicate the 64-bit address. The primary disadvantage with this approach is that it effectively requires multiple cycles in order to communicate the address to the controller. In particular, the process requires double buffering within a 32-bit address buffer, reading this buffer, and extracting the actual address. This overhead occurs for all addresses, even those that do not require 64-bit addressing. The process introduces inefficiencies within the fetching operations and causes delay in the performance of requests.
Accordingly it is desirable to provide a device and method that addresses the above-described problems.
SUMMARY OF THE INVENTIONA system, apparatus and method are provided for defining a plurality of modes for communicating variable size requests between a host system and a peripheral storage system controller. A first communication mode may be selected from the plurality of communication modes based on a size of memory and the bit length required to communicate a physical address associated with the memory. During runtime, a switch from the first communication mode to a second communication mode also may be performed in order to improve the efficiency of processing address requests at the storage system controller.
In one embodiment of the invention, a RAID controller and driver communicate in accordance with one mode selected from a plurality of available communication modes in order to improve the processing of an address request. A 32-bit mode and a 64-bit mode may be available and one mode is selected according to the length of the physical address of a message frame. For example, if the physical address is less than a threshold size then a 32-bit mode is used and if the address is larger than a threshold size then a 64-bit mode is used. The availability of these modes allows a system to more efficiently process varying address request sizes by reducing the number of I/O cycles required to process the address request.
A mode may be established through a handshake between the controller and the driver. In one embodiment, this handshake may occur at the time of initialization during which a particular mode is identified in which communication between the controller and driver is to occur. In another embodiment, a mode may be changed during runtime, which would require that there not be any pending commands and that a handshake between the devices occurs prior to switching the mode.
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
An apparatus and method for providing and switching between different communication modes is described. In one embodiment of the invention, a RAID controller and driver communicate in accordance with one mode within a plurality of available communication modes in order to improve the processing of an address request. A 32-bit mode and a 64-bit mode may be available and one mode is selected according to the length of the physical address of a message frame. For example, if the physical address is less than 4 gigabits then a 32-bit mode is used and if the address is larger than 4 gigabits then a 64-bit mode is used. The availability of these modes allows a system to more efficiently process varying address request sizes by reducing the number of I/O cycles required to process the address request.
A mode may be established through a handshake between the controller and the driver. In one embodiment, this handshake may occur at the time of initialization during which a particular mode is identified in which communication between the controller and driver is to occur. In another embodiment, a mode may be changed during runtime, which would require that there not be any pending commands and that a handshake between the devices occurs prior to switching the mode.
In the following description, for purpose of explanation, specific details are set forth in order to provide an understanding of the invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without these details. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into a number of different devices including personal computers, storage devices and network servers. The embodiments of the present invention may also be present in software, hardware or firmware. Structures and devices shown below in block diagram are illustrative of exemplary embodiments of the invention and are meant to avoid obscuring the invention.
Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
C. Overview
According to one embodiment of the invention, communication between the processor/driver 102 and controller 104 occurs in accordance with a mode of communication. This mode defines the parameters in which the processor/driver 102 and controller 104 communicate including the length of an address buffer in which the processor/driver provide a physical address of a message frame. By adjusting the length of the address buffer, the processing of I/O commands may be improved through matching buffer length to address length.
In one embodiment of the invention, a first mode having a 32-bit address buffer is defined and a second mode having a 64-bit address buffer is defined. Accordingly, if a system has a memory above a particular threshold that would require an address length not suited for a 32-bit buffer, the system may switch to the second mode and write the address within an effect 64-bit address buffer. This switching between modes allows a system to effectively address memories of varying sizes while reducing the number of cycles required to process a particular address request.
D. RAID Controller
Communication between the host processor 102 and controller 104 may include the use of one or more registers. These registers may include message registers, doorbell registers, and interrupt registers. The processor 102 may put a command in an inbound post queue (e.g., circular queue) after preparing a message frame in the host memory. If a physical address allotted to this message frame is greater than a particular value (e.g. 4 GB) then two address cycles are needed to send this frame to the controller 104. The use of two address cycles for a single command is called as Dual Addressing Scheme (“DAS”).
The RAID controller 200 and driver operate in one of a plurality of available modes. The mode initialization module 202 effectively controls the mode in which the RAID controller receives commands after initialization. In one embodiment, a host processor or driver may place a command in a queue at initialization that identifies a mode in which physical addresses are to be provided to the controller 200. During or after the RAID controller 200 is initialized, the mode initialization module 202 checks this queue to determine the appropriate mode of communication. The controller 200 will operate in this mode until it is notified of a mode switch during runtime or re-initialization.
In one embodiment of the invention, a communication mode between the RAID controller 203 and a driver or processor may be switched during runtime. In this embodiment, the runtime mode switching module 203 is signaled by a driver or processor that it is switching modes. In another embodiment, the runtime mode switching module 203 determines that a mode switch is appropriate and signals the driver or processor. In either embodiment, it is important that there are not any pending commands prior to the actual switching of a mode. For example, once a dual addressing scheme is enabled, a driver may write a particular bit in an inbound queue port for switching back to a single address scheme.
In one embodiment of the invention, a single address scheme is set as a default when the controller 203 boots up. If the physical address of the message frame is less than a particular value (e.g., 4 GB), then it may be right shifted a certain number of bits, such as 3 bits for making the driver/agent specify the number of frames to be read. If the physical address of the message frame is greater than a particular value (e.g., 4 GB), then the number of frames to be read is specified in a lower address.
If firmware state is MFI_STATE_FAULT (15), then it indicates that an internal firmware/hardware fault has occurred and the driver should not load any further commands. Further, whenever any fault occurs, the driver posts an operating system event indicating the fault condition of the controller 200. If firmware state is MFI_STATE_READY (11) or MFI_STATE_OPERATIONAL (12), then controller 200 posts the maximum possible number of outstanding commands, and the maximum possible number of scatter/gather elements (“SGE”) for any one command in the MFI_STATE register.
The above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above description, many variations will be apparent to one skilled in the art that would yet be encompassed in the spirit and scope of the invention. Accordingly, the scope of the invention is to be limited only by the following claims.
Claims
1. A storage controller that communicates with a host system, said storage controller comprising:
- a bus interface, coupled to a bus, on which commands from said host system are received;
- a command processor, communicatively coupled to said bus interface, that processes said commands from said host system;
- a communication mode initialization module, coupled to receive a communication mode initialization command from said host system, that sets a first communication address buffer length mode of said storage controller from a plurality of available communication address buffer length modes;
- a runtime communication mode switching module, coupled to said communication mode initialization module, that switches from said first communication address buffer length mode to a second communication address buffer length mode during runtime based on an address length of a memory address command such that said second communication address buffer length mode aligns an address buffer length of said storage controller with said address length of said memory address command, and does not manipulate individual bits to accommodate said changes in address length of said memory address command, said address length of said memory address command being a number of bits within said memory address command.
2. The storage controller of claim 1 wherein said storage controller controls a Redundant Array of Independent Disks.
3. The storage controller of claim 1 wherein said communication mode initialization module initiates a communication address buffer length mode in response to said host system writing a command in a queue.
4. The storage controller of claim 1 wherein said communication mode initialization module initiates a particular default communication address buffer length mode at initialization of said storage controller.
5. The storage controller of claim 1 wherein said first communication address buffer length mode defines a 32-bit word in an address buffer.
6. The storage controller of claim 1 wherein said first communication address buffer length mode defines a 64-bit word in an address buffer.
7. The storage controller of claim 1 wherein said second communication address buffer length mode defines a 64-bit word in an address buffer.
8. A method for establishing a communication mode between a storage controller and a host system, said method comprising:
- identifying a first bit length required to provide a physical address to a said storage controller;
- selecting a first communication address buffer length mode from a plurality of communication address buffer length modes, based on said identified first bit length such that said first communication address buffer length mode aligns an address buffer length of said storage controller with said identified first bit length; and
- switching at runtime from said first communication address buffer length mode to a second communication address buffer length mode based on a second bit length within a memory address command such that said second communication address buffer length mode aligns said address buffer length of said storage controller with said second bit length and does not manipulate individual bits to accommodate said changes in address length of said memory address command.
9. The method of claim 8 wherein said first communication address buffer length mode is established at initialization of said storage controller.
10. The method of claim 8 wherein said storage controller controls a Redundant Array of Independent Disks.
11. The method of claim 8 further comprising a step of said host system writing a command in a command queue to notify said storage controller of said selected first communication address buffer length mode.
12. The method of claim 11 wherein a driver for a storage system associated with said storage controller writes said command in said command queue.
13. The method of claim 8 wherein said first communication address buffer length mode defines a 32-bit length address buffer.
14. The method of claim 8 wherein said second communication address buffer length mode defines a 64-bit length address buffer.
15. A computer program product embodied on a non-transitory computer readable medium for establishing a communication address buffer length mode between a storage controller and a host system, said computer program product comprising computer instructions for:
- identifying a first bit length required to provide a physical address to said storage controller;
- selecting a first communication address buffer length mode from a plurality of communication address buffer length modes, based on said identified first bit length such that said first communication address buffer length mode aligns an address buffer length of said storage controller with said identified first bit length; and
- switching at runtime from said first communication address buffer length mode to a second communication address buffer length mode based on a second bit length within a memory address command such that said second communication address buffer length mode aligns said address buffer length of said storage controller with said second bit length and does not manipulate individual bits to accommodate said changes in address length of said memory address command.
16. The computer program product of claim 15 wherein said first communication address buffer length mode defines a 32-bit address buffer.
17. The computer program product of claim 15 wherein said second communication address buffer length mode defines a 64-bit length address buffer.
18. The storage controller of claim 1 wherein said runtime communication mode switching module ensures that there are no pending commands prior to switching from said first communication address buffer length mode to said second communication address buffer length mode.
19. The method of claim 8 further comprising a step for ensuring that there are no pending commands prior to switching from said first communication address buffer length mode to said second communication address buffer length mode.
20. The computer program product of claim 15 further comprising computer instructions for ensuring that there are no pending commands prior to switching from said first communication address buffer length mode to said second communication address buffer length mode.
5249279 | September 28, 1993 | Schmenk et al. |
5640600 | June 17, 1997 | Satoh et al. |
5680598 | October 21, 1997 | Farrell et al. |
5682509 | October 28, 1997 | Kabenjian |
5764938 | June 9, 1998 | White et al. |
5826074 | October 20, 1998 | Blomgren |
5828865 | October 27, 1998 | Bell |
5867645 | February 2, 1999 | Olarig |
5913045 | June 15, 1999 | Gillespie et al. |
6047120 | April 4, 2000 | Bell |
6047348 | April 4, 2000 | Lentz et al. |
6175884 | January 16, 2001 | Harriman et al. |
6179664 | January 30, 2001 | Tung et al. |
6189058 | February 13, 2001 | Jones et al. |
6260137 | July 10, 2001 | Fleck et al. |
6266755 | July 24, 2001 | Yeager |
6266778 | July 24, 2001 | Bell |
6381674 | April 30, 2002 | DeKoning et al. |
6609163 | August 19, 2003 | Nguyen et al. |
7058791 | June 6, 2006 | Hughes et al. |
20030086324 | May 8, 2003 | Higashiho |
20030196077 | October 16, 2003 | Henry et al. |
20030221038 | November 27, 2003 | Yoo et al. |
20050044290 | February 24, 2005 | Ishii |
20070028075 | February 1, 2007 | Holder et al. |
10214250 | August 1998 | JP |
2000020458 | January 2000 | JP |
2000204061 | July 2000 | JP |
2003281087 | October 2003 | JP |
- IBM Technical Disclosure NN9512485.
- IBM Technical Disclosure NN960839.
Type: Grant
Filed: Sep 22, 2005
Date of Patent: Aug 31, 2010
Patent Publication Number: 20070067501
Assignee: LSI Corporation (Milpitas, CA)
Inventors: Parag R. Maharana (Fremont, CA), Senthil M. Thangaraj (Fremont, CA), Gerald E. Smith (Suwanee, GA)
Primary Examiner: Henry W. H. Tsai
Assistant Examiner: Steven G Snyder
Attorney: Cochran Freund & Young LLC
Application Number: 11/232,927
International Classification: G06F 3/00 (20060101); G06F 12/00 (20060101);